Flat panel displays are widely used in a variety of applications, including computer displays. One suitable flat panel display is a field emission display. Field emission displays typically include a generally planar baseplate positioned beneath a faceplate. The baseplate includes a substrate having an array of surface discontinuities projecting from an upper surface. Conventionally, the surface discontinuities are conical projections, or "emitters" integral to the substrate. Contiguous groups of emitters may be grouped into emitter sets where the bases of the emitters in the emitter sets are commonly connected.
Typically, the emitters are arranged in an array of rows and columns, and a conductive extraction grid is positioned above the emitters. All, or a portion, of the extraction grid is driven with a voltage of about 30-120 V. The emitters are then selectively activated by applying a voltage to the emitters. The voltage difference between the emitters and the extraction grid produces an electric field extending from the extraction grid to the emitters. In response to the electric field, the emitters emit electrons.
The faceplate is mounted directly above the extraction grid, and includes a transparent display screen coated with a transparent conductive material to form an anode biased to about 1-2 kV. The anode attracts the emitted electrons. A cathodoluminescent layer covers the anode and faces the extraction grid to intercept the electrons as they travel toward the 1-2 kV potential of the anode. The electrons strike the cathodoluminescent layer, causing the cathodoluminescent layer to emit light at the impact site. The emitted light then passes through the anode and display screen where it is visible to a viewer. The light emitted from each of the areas thus becomes all or part of a picture element or "pixel." To individually control each of the pixels, current through each emitter or group of emitters is selectively controlled by a row signal and column signal through corresponding drive circuitry. To create an image, the control circuitry separately establishes current to each of the emitters or emitter sets.
The characteristics of the light produced in response to the emitted electrons depends, in part, upon the properties of the cathodoluminescent layer. For example, the cathodoluminescent layer may include a phosphor material that emits light over a wide range of wavelengths simultaneously. In some instances, substances are added to the phosphor material to control the wavelengths of emitted light thereby producing light of a desired color. One skilled in the art will recognize that a wide choice of colors are available. Where either of these types of materials contiguously coat a display region, images are produced by variations in light intensity at each pixel, disregarding chrominance information. Material for displaying images without color variations, such as material that substantially contiguously coats a region, will be referred to herein as a monochrome material. One skilled in the art will recognize that the term "monochrome" may refer to a single color material that emits over a narrow range of wavelengths or a full spectrum material that simultaneously emits over a wide range of wavelengths. For example, screens for black and white televisions emit full spectrum light at selected gray levels while screens in night vision goggles typically utilize green monochrome material.
Often, a cathodoluminescent layer will include several discrete subregions of color materials or "subpixels." Typically, such subregions are grouped into threes or "color triads" which include a red, a green and a blue subregion. Such screens can emit a variety of colors depending upon the relative activation levels of the red, green and blue subregions. Such relative activation levels are typically controlled in response to chrominance information in a video signal. Materials having selectable color emissions will be referred to herein as "color materials." It will be understood that such color materials typically include more than one type of material, such as triads of red, green and blue subregions.